2022 Fiscal Year Research-status Report
Investigation on the arrhythmogenecity of Nav1.5-TRPM4 channel complex
| Project/Area Number |
20K16126
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| Research Institution | Fukuoka University |
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Principal Investigator |
胡 耀鵬 福岡大学, 医学部, 助教 (40708476)
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| Project Period (FY) |
2020-04-01 – 2024-03-31
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| Keywords | Arrhythmogenicity / TRPM4 / Purkinje fibers |
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| Outline of Annual Research Achievements |
In this fiscal year, our focus was on investigating the arrhythmogenicity induced by gain-of-function mutations and pathological activation of TRPM4 in Purkinje fibers (PF). We conducted voltage-jump experiments in HEK293 cells expressing the E7K and Q854R TRPM4 mutants under ionomycin-perforated cell-attached recording to mathematically model the altered gating of the mutants. The results showed that the mutants had increased voltage- and Ca2+-sensitivities, leading to a stabilized open state. Using a modified Trovato PF model in 1D cable simulations, we demonstrated that enhancing the density/activity of mutant channels progressively reduced AP conduction velocity, eventually leading to complete conduction block. Furthermore, 2D simulations with HL-1 atrial cardiomyocyte and cardiac fibroblast models revealed that the gain-of-function mutants could generate complex patterns of anisotropic AP propagation characterized by various degrees of local conduction blocks, fission, meander and fusion of excitation fronts, and ectopic excitations, particularly in the presence of tissue heterogeneity. These complex patterns represent a significant trend towards arrhythmias. Ex vivo experiments were performed in Langendorff perfused hearts, and the results showed that the TRPM4 selective blocker, 9-phenanthrol, strongly suppressed ventricular tachycardias induced by mechanical stimulation of endocardial PFs exposed to ischemia-reperfusion injury. These findings suggest a potential involvement of overactive TRPM4 channels in PFs and their contribution to arrhythmogenicity.
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| Current Status of Research Progress |
Current Status of Research Progress
3: Progress in research has been slightly delayed.
Reason
Further validation of the present data through animal experiments is challenging and difficult.
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| Strategy for Future Research Activity |
Our work will focus on further characterizing the functional interaction between Nav1.5 and TRPM4 channels through experiments and simulations. We plan to use animal models and Langendorff experiments to investigate the relationship between TRPM4 and Nav1.5 expression/activities and their contribution to arrhythmogenicity.
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| Causes of Carryover |
According to our plan, research costs will be spent on animal experiments, consumables for cell culture, molecular biological, biochemical and electrophysiological experiments. We are contemplating submitting our work to certain academic journals.
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Research Products
(2 results)
